Reconstructing Early Paleogene forests, food webs and climate using the fossil leaves of Wyoming

November 6 (MONDAY!!)   Presented by Esther Pinheiro, University of Wyoming

The warmest point in the past 65 million years (since the demise of the dinosaurs) was 55 million years ago. The earth was 90-150 F warmer than today; the poles were ice free; sea level was significantly higher; animal and plant life changed dramatically. Why does this matter? Because there is general scientific agreement that on current trends the earth could well re-visit these conditions due to human caused global warming. By studying the fossil record of this time here in Wyoming we are able to learn how this ancient event may have occurred, and to study its affect on the earth. Fossil leaves offer particularly powerful insights into the world of that time.

Knowledge of the organization and host specificities of plant–herbivore food webs is important for understanding historical biodiversity patterns and the processes of their maintenance. The study of Paleogene ecological interactions allows us to better predict how modern ecosystems will respond to human caused global warming. We analyzed plant community structure and the impact of insect browsing on ancient floras from strata of the Wind River Basin and Bighorn Basin, central Wyoming, USA. We compared leaf compressions collected from the basin edge (4 sublocalities, 910 specimens) and basin interior (8 sublocalities, 1755 specimens) of the Wind River basin to the interior of the Bighorn Basin (7 sublocalities) to examine how differences in plant communities influence how they are browsed upon.

Differences in environment, plant distributions, and associated insect browsing were evident – some were anticipated, others unexpected. Causes are likely to have been paleoelevation, humidity, soil depth and type, and the abundance of taxa with nitrogen-fixing symbionts. Analyses of these data and their associated causes will be discussed, as well as how the data and causes will better enable researchers to model the affects of climate change on modern flora and fauna.